A bush pilot is hired for $250,000 to go to Mexico to free an innocent prisoner.

At the height of the frontier era, a train races through the Rocky Mountains on a classified mission to a remote army post. But one by one the passengers are being murdered, and their only hope is the mysterious John Deakin, who’s being transported to face trial for murder.

When half-breed Indian Yaqui Joe robs an Arizona bank, he is pursued by dogged lawman Lyedecker. Fleeing to Mexico, Joe is imprisoned by General Verdugo, who is waging a war against the Yaqui Indians. When Lyedecker attempts to intervene, he is thrown into prison as well. Working together, the two escape and take refuge in the hills, where Lyedecker meets beautiful Yaqui freedom fighter Sarita and begins to question his allegiances.